Tunable magnetron



7 I/Il/I/I/II/II/I/I/II/II; YIIII/I/IIII/(IlIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII/I/II/A INVENTOR CHAFLEJ V. l/TTZVV 0% ATTORNEY C V LITTON TUNABLE MAGNETRON Filed Aug. 31, 1946 I/IIIIIIIIIIIIIII/IA 'II/IIIIIIIII May 8, 1951 Patented May 8, 1951 TUN ABLE MAGNETRON Gharles V. Litton, Redwood City, Calif., assignor to Federal Telephone and Radio Corporation, New York, N. Y, a corporation of Delaware Application August 31, 1946, Serial No. 694,259

9 Claims.

This invention relates to magnetrons particularly to tunable magnetrons adapted to operate at very high frequencies.

At those frequencies at which distributed-constant circuit elements are employed, such as for example, coaxial lines or wave guides, certain magnetrons have been proposed whose central cathode is surrounded by a cylindrical anode, which latter has been grooved or provided with inwardly directed vanes to form tuned circuits therein. Such magnetrons are relatively cmplicated, require highly accurate spacing of the cathode in relation to the grooves, careful machining of numerous surfaces of the anode forming the tuned circuits, and fine adjustment of the various potentials and the electromagnetic force applied. These magnetrons are difficult to control and are not capable of being satisfactorily tuned over any substantial frequency range. In order to obtain the optimum operating conditions for a given magnetron, the space between the cathode and anode structure must be carefully adjusted. The optimum spacing cannot be readily predetermined in designing the magnetron and in the structures described, no means are provided for subsequent adjustment. Furthermore this spacing changes with the frequency of operation, and in tuning the magnetron it is desirable to likewise readjust this spacing (referred to hereinafter as: the interaction space).

An object of the present invention is the provision of an improved magnetron, particularly one adapted for use at said high frequencies. Another object is to provide a magnetron with a single vane defining two magnetron cavity resonators only.

Another object is the provision of a magnetron which is tunable over a range.

Another object is the provision of a magnetron in which the interaction space may be readily adjusted.

Another object is the provision of a magnetron characterized by simplicity of structure.

The above mentioned and other features and objects of this invention will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in connection with the accompanying drawings, wherein:

Fig. 1 is a schematic longitudinal section of a magnetron embodying my invention; and

Fig. 2 is a similar view taken in a plane revolved 90 from that of Fig. 1.

Referring now to the drawing, a cathode l is mounted by means of two leads 2 extending through insulators 3 in a metallic bellows G which is fastened to the end plate 5 on a metallic cylinder 6, which end plate 5 and cylinder 6 serve as part of the envelope of the magnetron. The envelope of the magnetron is completed by a glass disk I sealed in the cylinder 6 at a distance from the cathode I. Sealed through a slot in the glass disk I a metallic vane 8 projects towards the cathode I. The vane 8 divides cylinder 6 into two resonant cavities whose tuning is determined by the adjustment of a slidable metallic piston 9 which maybe in contact with the Walls of cylinder 6 and may be capacitively coupled to the vane 8, being slightly spaced therefrom. The vane tapers into the inner conductor III of a coaxial output line, although it will be appreciated that other output means, such as waveguide means may be employed. The cylinder 6 may be capacitively coupled by any suitable arrangement II to the outer conductor l2 surrounding inner conductor Ill, this capacitive arrangement serving to keep the D. C. potentials from the outer conductor I2.

To produce the required electrostatic field, the positive side of a source of potential I3 may be applied to cylinder 6 and vane 8, with the negative side thereof connected to the cathode I. Suitable means such as a choke coil It, may be employed to keep the radio frequency current out of the source I3. To produce the proper magnetic field, any suitable means, such as a magnet I5, may be provided. The operation of the device is similar to that of the conventional magnetron with a plurality of tuned or resonant circuits symmetrically arranged about the cathode. The magnetic field produced by N and S along the cathode I causes the electrons to follow spiral paths about the cathode. The electromagnetic field between the vane 8 and the outer cylinder 6 has an electric component that takes energy from some of the electrons. Those electrons which travel past the vane 8 in such phase as to take energy from the electric field are collected either by the vane 8 or the cylinder 6. The remaining electrons continue to follow spiral paths and give up energy to the electromagnetic wave in the resonators between B and 6 until they are captured by the cathode.

The tuning of the magnetron is accomplished by adjusting the sliding piston 9 which correspondingly changes the size of the resonant cavities I5 and ll. The bellows i is then moved to adjust the interaction; space to the optimum and maintained in position by some retaining means not shown. Both the electromagnetic and electrostatic fields may be further varied for proper adjustment.

While I have described about the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention.

I claim:

1. An electron space discharge device comprising a hollow metallic member, a single metallic element mounted within and spaced from the walls of said member substantially dividing said member into two cavity resonators, said element having a substantially straight end portion, electron emitting means, mounted in said hollow member in parallel relation to said end portion and means positioned adjacent said emitting means for causing said electrons to follow curved paths with respect to said metallic element, said electron producing oscillations in said cavity resonators.

2. An electron space discharge device comprising a hollow metallic cylinder along the longitudinal axis thereof, a flat plate mounted within said cylinder substantially dividing said cylinder into two cavity resonators, electron emitting means mounted in said cylinder parallel to said plate, and means positioned adjacent said emitting means for causing said electrons to follow curved paths with respect to said flat plate, said electrons producing oscillations in said cavity resonators.

3. An electron space discharge device comprising a hollow cylinder, a plate within said cylinder substantially dividing said cylinder alon the longitudinal axis thereof into two cavity resonators, electron emitting means mounted in said cylinder adjacent and parallel to an end of said plate, means positioned adjacent said emitting means for causing said electrons to follow curved paths with respect to said plate, said electrons producing oscillations in said cavity resonators, and a coaxial output line having its inner conductor coupled to said plate and its outer conductor coupled to said cylinder.

4. A magnetron comprising a hollow metallic member, a metallic element substantially dividing said member into two cavity resonators, electron emitting means mounted in said hollow member parallel to said metallic element, an envelope enclosing said emitting means, said hollow member and metallic element extending outwardly from said envelope, a plunger in said hollow member external to said envelope for tuning said cavity resonator, and magnetic field producing means positioned adjacent said emitting means for causing said electrons to follow curved paths with respect to said metallic element.

5. An electron space discharge device according to claim 1 wherein said electron emitting means includes a cathode mounted at a spaced distance from said metallic element, and means connected between said cathode and said hollow member for varying the spacing therebetween.

6. An electron space discharge device according to claim 3 wherein said plate and said inner conductor are coupled together by a tapered member.

7. An electron space discharge device according to claim 3 wherein said electron emitting means is a cathode, and wherein there are further provided a flexible bellows supported from said cylinder and means on said bellows for supporting said cathode, whereby the spacing between said cathode and said plate may be varied.

8. An electron space discharge device according to claim 3 further including piston means mounted within said member and adapted for effectively varying the tuning of said cavity resonators.

9. An electron space discharge device according to claim 3 further including adjustable means in said hollow member for varying th dimensions of said cavity resonators.

CHARLES V. LI'I TON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,037,977 Hansell Apr. 21, 1936 2,129,713 Southworth Sept. 13, 1938 2,167,201 DaIIenbach July 25, 1939 2,190,668 Llewellyn Feb. 20, 1940 2,247,077 Blewett June 24, 1941 2,278,210 Morton Mar. 31, 1942 2,407,974 Clifford et al Sept. 24, 1946 2,415,962 Okress Feb. 18, 1947 

